This invention relates generally to mattress foundation structures and more particularly to a box spring assembly of a type which utilizes non-coil springs. Box spring assemblies of this general type have been known since 1964, the first such spring assembly being disclosed in U.S. Pat. No. 3,286,281. Subsequently issued patents disclosing the same general type of box spring assembly are: U.S. Pat. Nos. 3,665,529; 3,680,157; 3,755,833; 3,824,639; 3,852,838; 4,060,862; 4,120,058; 4,131,961; 4,195,376; 4,218,790; 4,238,861; 4,251,892; 4,253,208; 4,339,834; 4,371,152; 4,398,765; 4,452,438; 4,470,584; 4,739,977; 4,779,293; 4,805,883; 4,867,424; 4,891,853; 4,921,228; and 4,932,535.
Box spring assemblies of the general type shown in the above list of patents, all of which are owned by the assignee of the present application, are advantageous with respect to conventional box spring assemblies using coil springs because they provide a desired stiffer foundation for the mattress and contain a reduced amount of wire. These box spring assemblies are also advantageous from the standpoints of prolonged service life, ease of assembly, and cost of manufacture.
Additional box spring assemblies of this general type are shown in U.S. Pat. Nos. 3,546,723; 3,596,299; 3,722,013; 3,825,960; 3,833,948; 3,835,485; 3,860,740; 3,990,131; 4,000,531; 4,559,654; and 4,730,357.
It is an object of the present invention to produce a box spring assembly in which the location of the spring modules is independent of the location of the long wires in the welded wire grid. It is another object of the present invention to enable a manufacturer to readily position the spring modules as desired on the frame of the assembly.
The present invention provides a box spring assembly that utilizes a welded wire grid and support springs which lock the grid into its proper position a predetermined distance above the frame assembly. The support springs of this invention are generally noiseless and have self-locking tops which enable the springs to be arranged in an "over and under" relationship with a single crosswire of the grid. Thus, the location and positioning of the springs is not dependent on the location of the long wires used in the welded wire grid. Such a construction enables the manufacturer to distribute the spring modules to provide support where it is particularly required in the specific box spring assembly. The support springs are also capable of being locked in a "dependent" relation with a pair of long wires in the grid. When so mounted the springs hold and secure the welded wire grid into a set position relative to the support frame.
The support springs of this invention are self-balancing in the sense that during assembly of the springs with the grid, all forces are in opposition to one another. Utilizing leaf spring tension in their upper ends, the springs are maintained in an assembled relation to the wire grid without the use of clips. To prevent bottoming out on the frame, the springs may also incorporate limited deflection characteristics.
In one embodiment of the invention, the springs are formed so that the upper torsion bar components are connected by a "straight diagonal" connecting wire. In a second embodiment, the springs utilize a zig-zag or "stairstepped" connecting wire. A third embodiment uses a curved connecting wire which gives the torsional bars and connecting wire an "S" shaped configuration.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.